Alkaline dry batteries generally have the following structure. A cylindrical positive electrode mixture containing a manganese dioxide powder or nickel oxyhydroxide as a positive electrode active material is disposed in a positive electrode case serving as a positive electrode terminal so as to closely adhere to the positive electrode case. In the center thereof, a negative electrode containing a zinc alloy powder as a negative electrode active material is disposed with a separator interposed therebetween. The negative electrode commonly used is a gel prepared by mixing a gelling agent such as sodium polyacrylate with an alkaline electrolyte.
In order to enhance the corrosion resistance of the negative electrode, it has been proposed to add an anionic surfactant, such as a polyoxyethylene alkyl ether phosphate in which the arkyl group has 6 or more carbon atoms (Patent Document 1) or a higher alcohol ether phosphate in which the arkyl group has 7 or more carbon atoms (Patent Document 2), to the gelled negative electrode as an anti-corrosive agent.
Meanwhile, phosphoric esters, which are anionic surfactants, are more likely to foam as the number of carbon atoms increases, and higher alcohol ether phosphates having about 13 carbon atoms in particular are high-foaming (Non-Patent Document 1).
Patent Document 1: Japanese Laid-Open Patent Publication No. Sho 55-69969
Patent Document 2: Japanese Laid-Open Patent Publication No. Sho 63-248064
Non-Patent Document 1: “Surfactant”, Yoneda Shuppan, page 149